diff --git a/app/common/ApiError.ts b/app/common/ApiError.ts
index 568f2d15..ac799494 100644
--- a/app/common/ApiError.ts
+++ b/app/common/ApiError.ts
@@ -23,6 +23,8 @@ export interface ApiLimit {
  * Structured details about an API error.
  */
 export interface ApiErrorDetails {
+  code?: ApiErrorCode;
+
   limit?: ApiLimit;
 
   // If set, this is the more user-friendly message to show to the user than error.message.
@@ -34,6 +36,9 @@ export interface ApiErrorDetails {
   memos?: string[];
 }
 
+export type ApiErrorCode =
+  | 'UserNotConfirmed';
+
 /**
  * An error with an http status code.
  */